1. Field of the Invention
The field of art to which this invention pertains is solid-bed adsorptive separation. More specifically, the invention relates to an improved process for separating a component from a mixture comprising an aqueous solution of a mixture of different components which process employs an adsorbent comprising a crystalline aluminosilicate bound with an amorphous inorganic binder material which selectively adsorbs a component from the feed mixture, the improvement which comprises the esterification of the crystalline aluminosilicate and/or binder material with an alcohol.
2. Description of the Prior Art
It is known in the separation art that certain crystalline aluminosilicates referred to as zeolites can be used in the separation of a component from an aqueous solution of a mixture of different components. For example, adsorbents comprising crystalline aluminosilicate are used in the method described in U.S. Pat. No. 4,014,711 to separate fructose from a mixture of sugars in aqueous solution including fructose and glucose.
It is also known that crystalline aluminosilicates or zeolites are used in adsorption processing in the form of agglomerates having high physical strength and attrition resistance. Methods for forming the crystalline powders into such agglomerates include the addition of an inorganic binder, generally a clay comprising silica and alumina to the high purity zeolite powder in wet mixture. The blended clay zeolite mixture is extruded into cylindrical type pellets or formed into beads which are subsequently calcined in order to convert the clay to an amorphous binder of considerable mechanical strength. As binders, clays of the kaolin type are generally used.
Zeolite crystal and binder material has long been known to have the property of gradually disintegrating as a result of continuous contact with water. It may be related to the surface migration and interaction between the charges of ions on the zeolite surface and in solution. In any event this disintegration has been observed as a silicon presence or contamination in the solution in contact with the zeolite and binder.
It is known, for example, from U.S. Pat. No. 2,657,149 that the surface of a silica substrate may be esterified by reaction with an alcohol to render the substrate hydrophobic, i.e. resist wetting by water.
We have discovered that the esterification of a clay bound zeolite will result in an improved separation process with minimization of the disintegration of the zeolite and binder and silicon contamination of the product.